In recent years, as a light emitting element, a light emitting diode (LED) has widely been used. Since the light emitting diode converts electric energy into light energy and has high efficiency and a long lifespan of 5 years or longer, it is possible to remarkedly reduce energy consumption and save maintenance cost, as a result, it has widely been in a next-generation lighting field.
The light emitting diode includes a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer. Light is generated from the active layer depending on current applied through the first conductive semiconductor layer and the second conductive semiconductor layer.
Meanwhile, the light emitting diode may be classified into a lateral-type light emitting diode and a vertical-type light emitting diode.
In the lateral-type light emitting diode, the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer are formed on a growth substrate and the second conductive semiconductor layer, the active layer, and the first conductive semiconductor layer are partially removed to partially expose the first conductive semiconductor layer in order to form an electrode layer. Therefore, an emission area is reduced to thereby deteriorate light efficiency.
Further, in the lateral-type light emitting diode, since the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer are disposed on the growth substrate, it is difficult to discharge heat due to the growth substrate having low thermal conductivity.
Further, in the lateral-type light emitting diode, since the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer are disposed on the growth substrate, it is difficult to discharge heat due to the growth substrate having low thermal conductivity.
On the contrary, in the vertical-type light emitting diode, since a first electrode layer is formed on the first conductive semiconductor layer and a second electrode layer is formed below the second conductive semiconductor layer, the active layer needs not to be removed in order to form the electrode layer, as a result, the emission area is not reduced. Accordingly, light efficiency may be improved as compared to the lateral-type light emitting diode.
Further, in the vertical-type light emitting diode, since heat is transferred through the second electrode layer, the heat is easily discharged.
Meanwhile, in the vertical-type light emitting diode, a large area is increased by allowing current that flows between the first electrode layer and the second electrode layer so as to increase the light efficiency.